An SLS Launched Cargo and Crew Lunar Transportation System Utilizing an ETLV Architecture

Before the end of the decade, the heavy lift capability that America once had during the Apollo era-- will return in the form of the SLS. Some, however, have argued that because of the former Space Shuttle's ability to deploy a 94 tonne aerospace plane plus up to 25 tonnes of useful cargo to LEO that , technically, the Shuttle was also a heavy lift vehicle. But even the earliest versions of the Space Launch System will be far more capable than the Space Shuttle in their ability to lift huge payloads into orbit. Unmanned versions of the SLS should be capable of deploying at least 70 tonnes of payload to LEO. And with an SLS derived upperstage, as much as 105 tonnes of cargo could be lifted to orbit. Even when deploying the 22 tonneMPCV (Multipurpose Crew Vehicle), the SLS should still be capable of simultaneously lifting an additional 45 to 80 tonnes of cargo to orbital space.

SLS crew launch and cargo launch vehicles; with an upper stage, the SLS would be capable of deploying nearly 39 tonnes of payload to Trans-Lunar Injection

Still there are those who argue that the SLS could be
deficient in its ability to deploy large crew landers and heavy cargo to the
lunar surface-- relative to the now cancelled Ares V
configurations. However, any deficiency in the lifting capability of the SLS could be easily compensated for by deploying-- fuel depots-- at the Earth-Moon
Lagrange Points, or in low Lunar orbit, or both. This might suggest to some NASA critics that the space agency would
have to spend substantially more of its limited funds in order to finance still another expensive component for its beyond LEO architecture-- in addition to funding the development of lunar crew and cargo vehicles.

However, if the next lunar landing vehicle developed for NASA is a-- single stage reusable spacecraft-- then aLagrange point fuel depotand alunar surface fuel depot could
both be derived from the reusable lunar lander. Such a reusable single staged lunar vehicle-- would already be inherently designed to refuel and store cryogenic fuels with zero boil-off. So deriving the fuel depot directly from the tanks utilized for the lunar landing vehicle could significantly reduce development cost. Additionally, the landing vehicle's reusability should also substantially reduce its
annual recurring cost for transporting humans to the lunar surface.

In an earlier post, I described a reusable single staged lunar landing vehicle concept that I called the ETLV-2 (Extraterrestrial
Landing Vehicle 2). The vehicle would be designed to take full advantage of a large 8.4 meter to 10 meter SLS payload fairing.

The ETLV-2 would utilize four CECE engines but just two common bulkhead tanks; each tank would be capable of storing up to 14 tonnes of liquid oxygen and hydrogen fuel. The tanks would utilize
a ULA type ofIntegrated Vehicle Fluid (IVF) technology plus NASA's breakthrough cryocooler technology to eliminate fuel boil-off and the waste of ullage gases. Such technologies could substantially reduce tank insulation and the overall weight of the space vehicle.

Basic components of the ETLV-2 lunar landing vehicle

The four
RL-10 derived CECE (Common Extensible Cryogenic Engine) engines should
enhance vehicle safety with engine out capability and reusability with up to 50 restarts capability. Vehicle development cost are further reduced in this concept by deriving the crew habitat module and airlocks from the light weight cryotanks. The pressurized crew hab should be tall enough to accommodate a crew of at least seven individuals, pressure suits, and small cargo on three floor levels. Such a large crew capacity would make the ETLV-2 potentially compatible with Commercial Crew launched vehicles since such privately operated vehicles should be capable of transporting as many as seven individuals to Earth orbit per flight. The ETLV-2 would, of course, also be capable accommodating the maximum crew of six aboard the MPCV.

The twin airlocks of the ETLV-2 would be utilized for giving humans access to the lunar surface through one airlock while the second airlock will allow small mobile robots and mobile vehicles access to the lunar surface on the opposite side of the vehicle. As an unmanned vehicle, the ETLV-2 could potentially be utilized for robotic sample retrieval missions to the lunar surface and possibly to the surfaces of the moons of Mars. In both cases, the regolith samples retrieved from deployed mobile robots would be returned to the Earth-Moon Lagrange points where a MPCV would dock with the unmanned ETLV-2 to pick up the samples for their journey to the Earth.

Fully fueled, the ETLV-2 should still weigh less than 38 tonnes and could, therefore, be deployed to TLI by the SLS upper stage.

ETLV-2 lunar landing vehicle: front, corners, & top views

While the ETLV-2 lunar lander would use only two long fuel tanks for its crewed missions to the lunar surface, the EML1 fuel depot concept proposed here would utilize five of the ETLV-2 tanks within a taller cruciform. The EML1 fuel depot could
potentially store more than 60 tonnes of cryogenic fuels. The L1 fuel
depot envisioned here would also be capable of perpetually storing up to
100 tonnes of water and be capable of converting the water into liquid
hydrogen and oxygen through solar powered electroysis and cryocooler
technology. The space fuel depot would also be capable of self deploying
itself practically anywhere within cis-lunar space and even into orbit
around Mars and Venus.

A single SLS launch would initially be required to deploy the fuel depot to EML1with
as much as 20 tonnes of cryogenic fuel. Since the ETLV-2 crew lander
would only require a few extra tonnes of additional fuel when it arrived
at L1, 20 tonnes should be enough fuel for perhaps three round trips
from L1 to the lunar surface-- if new mostly fueled ETLV-2 vehicle arrives
at L1 each time from Earth. However, MPCV launches by the SLS to EML1 should
be capable of carrying several tonnes of additional cargo. So several
tonnes of water cargo could be stored aboard the SLS upper stage
along with the MPCV. So any extraction of fuel from the EML1 depot for
crewed ETLV-2 lunar missions could be replaced by water deliveries
tagging along with the MPCV flights. An ETLV derived cargo lander (C-ETLV-4) would be used to deliver up to ten tonnes of payload to the lunar surface. The C-ETLV-4 would be primarily used for deploying the heavy machinery, ground vehicles, and crew habitats necessary to establish a permanently peopled water and fuel producing and exporting Lunar outpost-- similar to that envisioned by Dr. Spudis and Lovoie in their most recent papers.

Since I envision NASA
having at least two operational SLS launch padsby the early 2020s-- a
two launch scenario-- would be utilized for early manned missions to the
lunar surface. Such a launch infrastructure could also allow at least four heavy lift launches per year for both cargo and crew missions.

NASA's first manned lunar mission utilizing the SLS could send the ETLV-2 to TLI (Trans-Lunar Injection) where the remotely controlled unmanned crew lander
will separate from the SLS upper stage and utilize some of its fuel to reach EML1. The ETLV-2 will then dock with
the previously SLS deployed EML1 fuel depot in order to add the additional required fuel for its round trip journey
to the lunar surface and back to L1.

A second SLS launch, probably a few days later, would send the
MPCV plus a few tonnes of water to EML1. The MPCV will dock
with the fully fueled ETLV-2 and the crew (up to 6 people) will transfer
to the lunar lander for their journey to the Lunar surface and then,
eventually, back to L1 after their lunar mission is over. The EML1 fuel depot will dock with the water
tank, stored at the top of the SLS upper stage, and pump the water into the
fuel depot water compartment where it will eventually be converted into
liquid hydrogen and oxygen.

On their return trip to EML1, the
crew will transfer back to the MPCV for their return to Earth. Under this scenario, the
deployed ETLV-2 would remain at L1
until the EML1 fuel depot is finally being supplied with water from the lunar
surface for the manufacture of extraterrestrial fuel. This will allow a small fleet of reusable lunar landers to be deployed at EML1 by the SLS over just a few years for future use for manned lunar missions. Once an ETLV-2 vehicle is reactivated, it will refuel at L1 and then travel-- unmanned back to the lunar surface-- to ensure that the reusable vehicle is fully functional for human use again. The ETLV-2's CECE engines could be utilized for at least ten round trips before they would be required to be replaced-- or the landing vehicle retired.

I should note that the two launch scenario can also be utilized-- even if their is only one launch pad for the SLS (delaying the next launch from the pad for a few months)-- since the ETLV-2 would be equiped with cryocoolers capable of re-liquifying ullage gasses from is fuel tanks, providing zero boil-off of fuel for several months or even several years. However, limiting the SLS to just two launches per year would substantially slow down progress towards establishing manned outpost on the lunar surface and eventually on the surface of Mars. But there's really no logical reason to limit heavy lift launches to just two a year since NASA was able to launch as many as-- four heavy lift vehicles per year-- during the Apollo era and as many as nine Space Shuttle missions per year during the peak of the Shuttle era! Once the fleet of ETLV-2 landing vehicles are utilizing
lunar fuel resources for their operation and lunar water is being exported to the EML1 fuel depot from ETLV derived lunar tankers, NASA should then be able to incorporate the use of Commercial Crew vehicles as a cheaper component for sending astronauts to the Lunar surface. Reusable, ETLV-2 derived reusable Orbital Transfer Vehicles (OTVs) equipped with delta-v reducing aerobrakers should allow NASA to travel between LEO and EML1 a lot more cheaply. NASA astronauts and possibly even space tourist could then travel to the Moon by first taking a Commercial Crew vehicle to LEO where they would dock with an ETLV-2 derived OTV that utilizes lunar fuel stored at EML1 and possibly also at LEO. Once at EML1, the ETLV-2 would take the passengers down to the lunar surface.

So under this proposed scenario, the SLS and the MPCV could be used to set up a reusable transportation infrastructure that could eventually give passengers aboard private
Commercial Crew launch vehicles affordable and convenient access to the surface of the Moon-- just a few years after the SLS/MPCV/ETLV program begins.

Further details about
the ETLV components that will give Commercial Crew passengers access to the lunar surface will be discussed in more detail
in future post.

I assume that NASA will have a manned spaceflight budget that at least $8 billion a year once the SLS is fully operational and the RS-25E engines are ready(Obama inherited an $8.5 billion a year manned spaceflight budget from the Bush administration.

The cost per flight will, of course, will depend on how frequently the vehicle is flown. The Obama administrations concept of launching the SLS only once or twice every few years would be very expensive per flight. If the Shuttle program had been run that way then the cost per flight would have been well over $1.5 to $2 billion per mission.

NASA has estimated that the annual recurring cost of an SLS type of vehicle to be approximate 1.1 times as expensive as the Shuttle derived Sidemount Shuttle concept for four flights per year.

For four flights per year, NASA estimated the cost per flight for the Sidemount at more than $500 million per flight. That would probably put the cost of the SLS at nearly $600 million per flight. Four SLS flights per year would therefore cost less than $2.4 billion per year. That's certainly affordable within an $8 billion a year manned spaceflight related budget.

Because of its infrequent use, the launch of the ULA's Delta IV heavy cost over $400 million just to deploy 25 tonnes.

"The knowledge that we have now is but a fraction of the knowledge we must get, whether for peaceful use or for national defense. We must depend on intensive research to acquire the further knowledge we need ... These are truths that every scientist knows. They are truths that the American people need to understand." (Harry S. Truman 1948).